Polyolefin-based resins have advantages in their superior moldability, heat-resistance, mechanical characteristics, low specific gravity and the like; therefore, they are widely used in films, sheets and a variety of molded articles (such as structural parts). However, although the polyolefin-based resins per se generally have superior physical properties, there are cases where the use of a polyolefin-based resin is restricted depending on a certain type of application since the intrinsic superior performance of the resin cannot be attained.
This defect arises from the crystallizability of the polyolefin-based resins. In order to improve the crystallizability of a polyolefin-based resin to better the resin transparency and also to provide heat-resistance and mechanical strength, a variety of crystal nucleating agents are widely used. In addition, it is known that the crystallization of a polyolefin-based resin during molding is made controllable by adding a certain compound or composition to the polyolefin-based resin. In general, a polyolefin-based resin whose crystallizing action is facilitated may attain advantages in, for example, that the molding cycle time is shortened, that the transparency of the molded articles of the polyolefin-based resin is improved, and that the heat-resistance and physical characteristics are improved. Examples of such crystal nucleating agent include metal carboxylates such as sodium benzoate, aluminum 4-tert-butyl benzoate, sodium adipate, disodium-bicyclo[2.2.1]heptane-2,3-dicarboxylate; phosphoric ester metal salts such as sodium-bis(4-tert-butylphenyl)phosphate, sodium-2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate and lithium-2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate; and polyalcohol derivatives such as dibenzylidene sorbitol, bis(methylbenzylidene)sorbitol and bis(dimethylbenzylidene)sorbitol.
Further, it is also widely known to add an amide compound in order to improve the properties of a polyolefin-based resin. For example, Patent Document 1 proposes to blend a fatty acid diamide compound of phenylenediamine in order to inhibit deterioration of polypropylene which comes into contact with a heavy metal such as copper, and demonstrates the deterioration-inhibiting effect of the heavy metal. Further, Patent Document 2 discloses that the heat-sealing property and transparency are improved by blending a bis-amide compound to a polyolefin polymer containing polybutene-1 at an amount not less than 5% by mass. Furthermore, in Patent Document 3, it is disclosed that a crystalline polypropylene-based resin composition containing a large amount of β-crystal is obtained by adding an amide compound obtained from diamine and monocarboxylic acid to polypropylene. Still further, proposed in Patent Document 4 is a compound obtained by allowing naphthalene dicarboxylic acid or biphenyl dicarboxylic acid to react with monoamine. Still further, Patent Document 5 discloses a polypropylene resin composition whose crystallization temperature is improved by adding two or more urea-based compounds selected from monourea derivatives and diurea derivatives.
Still further, it is also known to use a hydrazide compound in order to improve the transparency of a polyolefin-based resin and to provide heat-resistance and mechanical strength. As an example of such resin using a hydrazide compound, Patent Document 6 describes a polylactic acid-based resin in which a hydrazide compound whose structure have phenol is used as a crystal nucleating agent. In addition, in Patent Document 7, it is described that the crystallization temperature of a polylactic acid-based resin composition is improved by blending to the polylactic acid an amide compound selected from chain amide, cyclic amid, chain hydrazide and cyclic hydrazide. In Patent Document 8, it is proposed to use, in a polylactic acid-based resin, a plasticizer constituted by an aliphatic ester derivative or aliphatic polyether derivative and a hydrazide compound such as octanedicarboxylic acid dibenzoyl hydrazide as the organic crystal nucleating agent in combination. Further, Patent Document 9 proposes to use a hydrazide compound in order to inhibit the release of aldehyde from the polypropylene material which was made transparent by dibenzyliden sorbitol. Still further, described in Patent Document 10 is to utilize a hydrazide compound such as N,N′-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine as the heavy metal inactivator in a crystalline polypropylene resin composition.
In addition, as a method of improving the crystallizability of a polyolefin-based resin, it is also known to use a hydrazone compound. As an example of such resin using a hydrazone compound, Patent Document 11 describes a polyacetal resin composition in which a hydrazone compound is used. Patent Document 11 describes the effects of inhibiting the generation of formaldehyde originated from the polyacetal resin and preventing mold deposit and bleed out. Further, in addition to the aforementioned Patent Document 11, compounds having a hydrazone structure are known to be used as a photopolymerization initiator or as raw material of polyurethane.
However, in the Patent Document 11, there is no description at all regarding the effects of the hydrazone compound to facilitate resin crystallization. In addition, conventionally, there is no known case where a hydrazone compound is applied to a polyolefin-based resin.
Incidentally, crystalline synthetic resins such as polyethylene, polypropylene, polybutene-1, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide and polyamide have problems in that the mold cycles are delayed due to the slow crystallization rate after heat-melt molding and that resin contraction may occur due to the further progress of crystallization after heat molding. In addition, these crystalline synthetic resins have defects in that, because of the generation of large crystals, the strength is not sufficient and the transparency is poor.
These defects also arise from the crystallizability of the synthetic resins, and it is known that these defects are overcome if the crystallization temperature of the synthetic resin could be improved, thereby allowing fine crystals to promptly form.
In order to solve the aforementioned defects, it is known to add a crystal nucleating agent or a crystallization promoter to the resin, and conventionally, carboxylic acid metal salts such as aluminum 4-tert-butyl benzoate and sodium adipate; acidic phosphoric ester metal salts such as sodium-bis(4-tert-butylphenyl)phosphate and sodium-2,2′-methylenebis(4,6-di-tert-butylphenyl)phosphate; and polyalcohol derivatives such as dibenzylidene sorbitol and bis(4-methylbenzylidene)sorbitol have been used.
Among those compounds, cyclic phosphoric acid ester metal salts of alkylidene bisphenols described in Patent Documents 12 and 13 have prominent effects and are, therefore, widely used.
In addition, by using these compounds in combination with other metal compound(s), it has been attempted to improve the effects of a resin. For example, Patent Document 14 discloses a method in which, in order to prevent a decrease in the resin rigidity when an aromatic phosphoric acid alkali metal salt-based nucleating agent and a carboxylic acid alkaline-earth metal salt such as calcium stearate are used in combination, a hydrotalcites or a carboxylic acid alkali metal salt is used in place of the carboxylic acid alkaline-earth metal salt.
In addition, Patent Documents 15 and 16 disclose a method in which a cyclic organic phosphoric acid ester metal salt and a metal salt (the metal belonging to the Periodic Table Group II) of aliphatic carboxylic acid are used in combination, and Patent Documents 17 and 18 disclose a method in which an acidic organic phosphate compound and an aliphatic carboxylic acid metal salt are used in combination. Disclosed in Patent Document 19 is a method in which, when a cyclic organic phosphoric acid ester metal salt is used, in order to prevent a decrease in the pH during the immersion into hot water after carrying out radiation irradiation as a post-treatment, a hydroxide of alkali metal, alkaline-earth metal or aluminum-group metal is used in combination. Patent Documents 20 to 22 disclose a method in which a basic aluminum salt of aromatic phosphodiester is used to improve the processability and heat-resistant rigidity of highly rigid propylene-based resins. Disclosed in Patent Document 23 is a method in which a basic aluminum salt of aromatic phosphodiester and a carboxylic acid alkali metal salt are used in combination, and Patent Documents 24 and 25 disclose a method in which a polyamine-based amide compound is blended to a crystalline synthetic resin such as polyolefin resin.